Quaternized tertiary aminomethyl acrylamide polymer microemulsions with improved performance

ABSTRACT

Quaternized tertiary aminomethyl acrylamide polymer emulsions are treated by 1) adjusting the pH to about 3.6 to about 4.8, 2) adding a formaldehyde scavenger, 3) adjusting the water content of the aqueous phase to result in about 10-45 weight percent of quaternized aminomethylated acrylamide polymer and 4) heating the resultant emulsion at from about 40° C. to about 80° C. for about 3 to about 20 hours so as to render them more stable, capable of inversion in water independent of water temperature or pH of the medium flocculant and superior dewatering ability.

This is a continuation of application Ser. No. 08/018,858, filed on Feb.12, 1993, now U.S. Pat. No. 5,627,260, for QUATERNIZED TERTIARYAMMINOMETHYL ACRYLAMIDE POLYMER MICROEMULSIONS WITH IMPROVEDPERFORMANCE.

The present invention relates to flocculants. More particularly thepresent invention relates to flocculants prepared as acrylamide polymermicroemulsions. Most particularly, the present invention relates toquaternized tertiary aminomethyl acrylamide microemulsions.

BACKGROUND OF THE PRESENT INVENTION

The use and development of synthetic polymers as flocculants hasprogressed and evolved since their introduction in the early to mid1950's. In use flocculants provide the ability to flocculate solidssuspended in a liquid medium, usually aqueous, to form a distinct entitycapable of being separated from that medium.

Generally it is believed that the mechanism whereby the destabilizationof ionic suspended solids occurs is by the neutralization of the chargeon such solids which contributes significantly to their suspensionstability. Mere neutralization of the charge of such solids, due totheir small size, is often insufficient to enable their efficientseparation from the liquid medium in which they are suspended and it hasbeen long recognized that synthetic polymers are helpful inagglomerating such solids into entities commonly referred to asflocculated solids or flocs. These precipitate like flocs may then beseparated from the liquid medium in which they are contained for variousreasons and purposes. In the area of water purification, such techniquesare used to remove materials undesirable for inclusion in dischargewaters and hence find their utility in the removal of materials from thefinal product of a purification process. In contrast, in the area ofpaper manufacture, such techniques are used in a similar way to includewithin the paper slurry solids, and hence the resulting paper, materialsthat would otherwise be lost from the paper during the water removalphase of its manufacture and which may also inhibit the efficiency ofdewatering during that phase.

Most effectively, the source of charge destabilization of suspendedsolids may be incorporated into the synthetic polymer molecule by theuse in the formation of the polymer of monomers having moieties, or bymodifying polymers to provide such moieties on the polymers, whichmoietes contain an ionic pair which upon addition of the polymer to anaqueous medium, dissociate to result in the polymer itself carrying acharge. Thus, polymers useful in flocculation have developed to presentday being high molecular weight polymers which in the presence of waterform a polymeric flocculant medium to provide a high content ofcationically charged sites combining the ability to both destabilizesuspended solids and to physically link them together into insolubleentities thereby separating them from the liquid medium in which theywere contained.

As indicated above, a clear line of distinction must be drawn betweencharge bearing synthetic polymeric flocculant materials and syntheticpolymers having charge contributing moieties for it is not until suchmoieties undergo disassociation that such polymers can have the desiredflocculant activity.

One of the most significant advances in synthetic polymers useful inflocculant applications was disclosed in commonly assigned U.S. Pat. No.4,956,399. In that patent there was disclosed a process using an inversemicroemulsion to form Mannich acrylamide polymers, their use asflocculants and specific compositions comprising emulsion microparticlescontaining (alk) acrylamide polymers substituted with tertiaryaminomethyl groups and having an average particle size of from about 200to about 4000 Å, about 0.02 to about 0.4 μm, in diameter. Theretofore,high molecular weight Mannich polyacrylamides (Mannich PAMs), while wellknown and used in a variety of flocculant applications, were associatedwith major drawbacks arising from cross-linking of the Mannichpolyacrylamides which was particularly severe when polymer solids wereincreased.

Several approaches had been tried to overcome these problems. Oneapproach was to make the Mannich PAMs at the site of use by invertinghigh solids inverse emulsion PAMs in water containing dialkylamines andformaldehyde. U.S. Pat. No. 4,021,394 and U.S. Pat. No. 4,022,741describe continuous processes for the preparation of Mannich PAMs whichentails inverting an inverse emulsion PAM in a process stream containingformaldehyde and a secondary amine and subjecting the stream toturbulence by in-line mixing to produce a 1-15% aqueous solution ofMannich PAM. This approach, however, suffered from the need to storemultiple chemicals on site and from the problems inherent in runningchemical reactions at such locations. Another approach had been toprepare dry Mannich PAMs, as described is U.S. Pat. No. 3,864,312; U.S.Pat. No. 3,539,535 and U.S. Pat. No. 3,790,529 or blends of dry PAMswith dry, low-molecular weight Mannich-base forming compounds which,when dissolved in water, react to produce Mannich PAMs, as described inEPO Patent No. 0,210,784. These approaches, in general, suffered fromcross-linking problems, the reversibility of the Mannich reaction, thedifficulty and length of time required to dissolve high molecular weightpolymers, and other problems. Another approach was to make the MannichPAM in inverse emulsions, such as described in U.S. Pat. No. 3,979,348;U.S. Pat. No. 4,093,542 and U.S. Pat. No. 4,010,131. While this approachproduces a product with substantially higher solids, the averageemulsion particle size thereof ranges from about 10,000-20,000 Å, about10 to about 20 μm, in diameter, and consequently, cross-linking of themany polymer chains in each emulsion particle renders the polymers lesseffective. The cross-linking rate of such polymers can be reducedsomewhat by adding fairly large quantities of stabilizers, such asdescribed in U.S. Pat. No. 4,113,685 and U.S. Pat. No. 4,073,763, butcross-linking continues and such products thus possess a very limitedshelf life.

Accordingly, there existed a need for a Mannich acrylamide polymer whichcould be prepared at high solids levels without extensive interpolymercross-linking such that it could be economically transported and easilyhandled by the end user without the need for any on-site preparation.

As discussed in U.S. Pat. No. 4,956,399, it was discovered that Mannichacrylamide polymers, produced in the form of inverse microemulsions,gave superior performance relative to the Mannich acrylamide polymers ofthe then prior art and could be conveniently prepared at high solidscontent while maintaining a very low bulk viscosity. As disclosed, incontrast to solution and inverse emulsion Mannich acrylamide polymers ofthe then prior art which contained large quantities of polymer moleculesin the same aqueous environment, the Mannich acrylamide polymers asmanufactured in the microemulsion process in the aforesaid patent areisolated as individual, or at most, several, polymer molecules in eachaqueous microemulsion micelle. Thus, the problem of large scaledebilitating interpolymer cross-linking inherent in the solution andinverse emulsion products of the prior art was overcome.

Additionally, in contrast to the high bulk viscosities of the morestable dilute solution acrylamide polymers of the prior art, themicroemulsion produced Mannich acrylamide polymers disclosed in thatpatent could be made at high solids levels while still maintaining anextremely low bulk viscosity.

Such a Mannich acrylamide polymer composition satisfed a long felt needand constituted a notable advance in the art. The methods of manufactureof such polymers, the polymers and their use are incorporated herein byreference to the aforesaid U.S. Pat. No. 4,956,396 as well as U.S. Pat.Nos. 4,956,400; 5,037,863; 5,037,881 and 5,132,023.

Interestingly, it has been observed that the manufacture of the abovediscussed polymers resulted in them being in what is believed to be apredisolved form within the aqueous microemulsion particle. By this ismeant that the polymer is present in the microemulsion droplet in ahydrated form which is advantageous in the make-up of a syntheticpolymeric flocculant medium for use in flocculant applications.

As indicated above, a line of distinction must be drawn between chargebearing synthetic polymer flocculant materials and synthetic polymershaving charge contributing moieties for it is not until the latter iscontacted with an aqueous environment that the charge neutralizingfunction of the polymer molecule is available for use. A number ofresearchers have made observations regarding the availability oftheoretical charge, some postulating that availability as a measure ofpolymer dissolution. While there might be a relationship between thetwo, for a given molecule under a given circumstance, the inavailabilityof theoretical charge has no predictive value as to degree ofdissolution, as factors such as stearic hindrance of the titrant on anotherwise soluble material could yield data indicative of a degree ofcharge unavailably. Similarly, accumulation of the titrant on theotherwise water-soluble polymer can itself render it insoluble in muchthe same way as the mechanism of flocculaion.

It has long been known that the availability of the theoretical chargeon a polymer can be affected by stearic hindrance. Thus, branching thathas occurred in prior art water soluble polymers, to the extent suchbranching exists, affects the degree to which ionic sites can beaccessed especially if the moiety of opposite charge is of any size.This is true whether or not the polymer is soluble or is cross-linked tothe point that it becomes insoluble which, in the case of the latter,has been present to varying degrees in prior art polymers for decades.

As discussed above in the case of Mannich polyacrylamides, excessivecross-linking, in particular, intermolecular cross-linking, has beenlong seen as detractive of polymer performance and it is believed that amajor contribution was the unavailability of charge sites or theformation of water-insoluble water swellable gels.

The polymers produced by reverse phase microemulsion polymerization areconveniently employed as flocculants prepared in the form of diluteaqueous solutions to form a synthetic polymeric flocculant medium. Thesesolutions are prepared by inverting the microemulsion into water,optionally in the presence of a breaker surfactant, or by recovering thepolymer from the microemulsion, such as by stripping or by adding themicroemulsion to a solvent which precipitates the polymer, e.g.isopropanol or acetone, filtering off the resultant solids, drying andredispersing in water. The microemulsion can also be stripped toincrease the percentage of polymer solids thereof.

Concentrating dispersions of suspended solids can be carried out byadding an effective amount of the polymer in solution form (i.e. aflocculant medium) to the suspension to remove water therefrom andproduce an effluent of desired characteristics.

The flocculant media are useful in facilitating a wide range ofsolid-liquid separation operations. The cationic polymers may be used inthe dewatering of biologically treated suspensions, such as sewage andother municipal or industrial sludges, the drainage of cellulosicsuspension such as those found in paper production, e.g. paper waste,and the settlement of various suspensions, i.e. refinery waste, foodwaste etc.

Despite the many advantages of the microemulsion formed polymersreferred to above, commercial experience has shown opportunities forimprovements. In particular, the amino methylated acrylamide polymermicroemulsions have suffered from insufficient stability at elevatedtemperatures and problems associated with ageing of the microemulsionsynthetic polymer flocculant material independent of the temperature orpH of said medium making them unacceptable for some specificapplications depending on local conditions.

As indicated above, polymers produced by microemulsion reverse phasepolymerization can be employed as dilute solutions to form a syntheticpolymeric flocculant medium. In practice, the microemulsion is invertedinto a large volume of water stripping the continuous oil phase from theaqueous micro droplets containing the polymer which is then mixed toform the diluted solution. The resulting solution is then aged tomaximize the expected performance from the medium. While in most casesthis can be accomplished in a relatively short period of time, it hasbeen found that under certain conditions of temperature and alkalinitylonger periods of aging are required which may necessitate theinstallation of storage tanks that may not be easily accommodated ordesired at the user's site. In the alternative, it may be required toadjust either the temperatures and/or pH of the diluent water, one orboth of which may be unacceptable to the user. The alternative of usingthe product without sufficient aging is that less than optimum flocs areobtained with the flocs sometimes being somewhat fragile or at the leastan uneconomic use of the polymer. In such cases, the polymer isgenerally rejected for that particular application. Interastingly, ithas been found that this diminished performance is not related to a lackof solubility of the polymer, which is believed already solubilized inits microparticle environment prior to inversion. Thus a need exists foran improved polymer having less dependence on temperature and pH oralkalinity for proper aging.

U.S. Pat. No. 3,988,277 teaches the stabilization of aqueous solutionsof Mannich polymers against viscosity increase and gelation by theaddition of an aldehyde scavenger thereto. Suitable scavengers includehydrazine, ammonia, morpholine, guanidine, dimethylamine and urea. Thepatent, however, fails to teach microemulsions and does not recognizethe necessity of adjusting the pH to the range claimed herein. Thepatent also is silent with respect to the polymer concentration and theneed for further heating after the scavenger addition.

Phillips et al., U.S. Pat. Nos. 4,010,131, and 4,079,027 disclosetreating inverse emulsions or solutions of quaternary modifiedacrylamides with halogen free oxygen containing inorganic acids such assulfurous acid, followed by heating to stabilize the quaternary modifiedemulsions. The patentees teach that sulfurous acid is used both toadjust the pH of the emulsion and as a formaldehyde scavenger. Thereferences do not teach that the heat-treated inverse emulsion willinvert in water independent of temperature and alkalinity. Thereferences do teach, however, that improved storage stability andcationic charge are obtained, however, the inverse emulsions describedmust be inverted at alkaline pH of 8.0. The patents teach that anadjustment of the emulsion pH between 0-6 is required, however, whenthis teaching is applied to quaternary Mannich microemulsions (QMM), theproduct fails to fully age independent of temperature and pH. Thus,these references fail to teach the critical pH range claimed herein andalso are devoid of any teaching of the necessity to adjust the waterconcentration of the aqueous phase of the microemulsion.

U.S. Pat. Nos. 4,113,685 and 4,179,370 disclose the stabilization ofMannich acrylamide polymer emulsions by adding thereto 1) awater-soluble salt of an amine, alone or 2) in association with an amineor ammonia, or 3) an ammonium salt of a mineral acid plus ammonia or 4)a carboxylic acid amide. The patentees, however, are silent with regardto the pH to which the emulsions are adjusted by the addition of theseadditives and do not recognize the advantages exhibited by the instantinvention by including a formaldehyde scavenger, adjusting the polymersolids content of the aqueous phase of the emulsion and heating theresultant emulsion for a specific length of time. The referenced patentsthus fail to teach the instantly claimed process.

U.S. Pat. Nos. 4,120,840 and 4,195,003 disclose that the use oforthophosphorous acid provides an odorless and effective formaldehydescavenger as well as pH adjuster. The invention teaches a method forstabilizing water-in-oil emulsions of polytrimethylaminomethylolacrylamide using orthophosphorus acid, but did not produce asatisfactory emulsion when applied to quaternary Mannich microemulsionsas judged from the standard discussed hereinafter.

Canadian Patent 1,204,535, teaches the use of sodium bisulfite as bothan acid pH adjuster and formaldehyde scavenger prior to alkylatingpartially cationically modified acrylamide polymer emulsions. Theproducts disclosed in this patent invert in water having a pH about 8.0or greater, however, when the teachings of this patent are applied tomicroemulsions, they fail to produce products which invert in water ofany temperature and alkalinity.

None of the prior art teachings provide a method for producing aquaternized tertiary aminomethyl acrylamide polymer microemulsion (QMM)which successfully inverts in water independent of the pH andtemperature of the water and also provide improved dewateringcharacteristics.

SUMMARY OF THE PRESENT INVENTION

According to the present invention there is provided a method fortreating a quaternized amino methylated acrylamide polymer microemulsion(QMM) comprising:

(a) adding to said quaternized amino methylated acrylamide polymermicroemulsion:

(i) acid, or a combination of acids, in an amount sufficient to providea pH of from about 3.6 to about 4.8 in the resulting emulsion;

(ii) from about 0.01 to about 30 mole percent of a formaldehydescavenger compound based on the total moles of quaternized aminomethylated acrylamide polymer microemulsion; and

(iii) water in an amount such that the aqueous phase of the resultingmicroemulsion comprises from about 10 to about 45 weight percent ofquaternized amino methylated acrylamide polymer microemulsion; and

(b) heating the microemulsion obtained in step (a) to a temperature offrom about 40° to about 80° C. for from about 3 to about 20 hours.

Additionally provided for herein are improved polymers produced by theabove stated method as well as methods of flocculating suspended solids.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The compositions treated by the process of the present inventioncomprise (alk)acrylamide polymer-containing microemulsions, the(alk)acrylamide polymer being substituted with at least about 1 molepercent of tertiary aminomethyl groups and having an average particlesize of from about 200 to about 4000 Å in diameter and are generallyprepared by an inverse microemulsion polymerization process, such astaught in U.S. Pat. Nos. 4,521,317; 4,956,399; 5,037,881; 5,093,009hereby incorporated by reference.

The backbones of the acrylamide polymers used in the process of thepresent invention may comprise units of such (alk)acrylamides asacrylamide, methacrylamide, ethacrylamide and the like. The backbones ofthe acrylamide polymers invention may also comprise an (alk)acrylamidecopolymerized with a cationic or non-ionic, water-soluble, ethylenicallyunsaturated comonomer in amounts up to about 90%, by weight.Water-soluble, anionic comonomers may also be used in substantiallylower amounts.

Useful cationic comonomers include diallyl dialkylammonium chlorides,N,N-dialkylaminoalkyl(meth)acrylates,N,N-dialkylaminoalkyl(meth)acrylamides, salts, quaternaries and mixturesthereof.

Anionic comonomers of the present invention may comprise acrylic ormethacrylic acid, fumaric acid, crotonic acid, maleic acid, saltsthereof; 2-acrylamido-2-methylpropane sulfonic acid; styrene sulfonicacid and their salts and the like.

Water-soluble, non-ionic comonomers generally comprise N-vinylpyrrolidone, N,N-dialkylmethacrylamides, hydroxyalkyl methacrylates;N-vinylformamide, and the like. Small quantities, i.e., up to about 10%by weight of other copolymerizable comonomers, such as methyl acrylate;methyl methacrylate; acrylonitrile, vinyl acetate, styrene, etc. mayalso be used.

In general, microemulsion polymerization processes are conducted by (i)preparing a monomer microemulsion by mixing an aqueous solution ofwater-soluble monomers with a hydrocarbon liquid containing anappropriate surfactant or surfactant mixture to form an inversemicroemulsion comprising small aqueous monomer solution dropletsdispersed in the continuous oil phase and (ii) subjecting the monomer inthe aqueous phase of the microemulsion to polymerization.

Suitable monomers are non-ionic, anionic and/or cationic and are asdefined above. The aqueous monomer solution may contain suchconventional additives as are desired. For example, the solution maycontain chelating agents to remove polymerization inhibitors,chain-transfer agents, pH adjusters, initiators and other conventionaladditives.

In order to obtain an inverse microemulsion, it is generally necessaryto use particular conditions whose main parameters are as follows:surfactant concentration, HLB of surfactant or surfactant mixture,temperature, nature of the organic phase and composition of the aqueousphase.

Essential to the formation of the microemulsion which may be defined asa transparent and thermodynamically stable solution comprising twoliquids insoluble in each other and a surfactant, in which the micellesare usually 1000 Å or less in diameter, is the selection of appropriateorganic phase and surfactant.

The selection of the organic phase has a substantial effect on thesurfactant concentration necessary to obtain the inverse microemulsionand may consist of a hydrocarbon or hydrocarbon mixture. Isoparaffinichydrocarbons or mixtures thereof are the most desirable in order toobtain inexpensive formulations. Typically, the organic phase willcomprise mineral oil, toluene, fuel oil, kerosene, odorless mineralspirits, mixtures of any of the foregoing and the like.

The ratio, by weight, of the amounts of aqueous phase and hydrocarbonphase, is chosen as high as possible, so as to obtain, afterpolymerization, a microemulsion of high polymer content. Practically,this ratio may range, for example, from about 0.5 to about 3:1, andusually approximates 1:1.

The one or more surfactants are selected in order to obtain an HLB(Hydrophilic Lipophilic Balance) value ranging from about 7 to about 12.Outside this range, formation of inverse microemulsions generally arenot attained. In addition to the appropriate HLB value, theconcentration of surfactant must be such as to form an inversemicroemulsion. Too low a concentration of surfactant leads to theformation of standard inverse macroemulsions and too high aconcentration results in increased costs and does not impart anysignificant benefit. Typical surfactants useful may be anionic, cationicor nonionic and include sorbitan monooleate, polyoxyethylene(20)sorbitan monooleate, sodium dioctylsulfosuccinate,oleamidopropyldimethyl amine, sodium isostearyl-2-lactate and the like.

Polymerization of the microemulsion may be carried out in any mannerknown to those skilled in the art. Initiation may be effected with avariety of thermal and redox free radical initiators, includingperoxides, e.g., t-butyl peroxide; azo compounds, e.g.,azobisisobutyronitrile; inorganic compounds, such as potassiumpersulfate and redox couples, such as ferrous ammonium sulfate/ammoniumpersulfate. Initiator addition may be effected any time prior to theactual polymerization per se. Polymerization may also be effected byphotochemical irradiation processes, such as ultraviolet irradiation orby ionizing irradiation from a cobalt 60 source.

It is possible to perform the Mannich substitution reaction at variousstages in relation to the inverse microemulsion polymerization. Theformaldehyde and secondary amine may be added after the inversemicroemulsion polymerization of the (alk)acrylamide and then reactedwith the resultant polymer to form the tertiary aminomethyl group on the(alk)acrylamide polymer backbone. It is also possible to react the(alk)acrylamide monomer with the formaldehyde and secondary amine priorto the inverse microemulsion formation and before polymerization of themonomers. Also contemplated, is adding the formaldehyde and secondaryamine to the aqueous solution prior to polymerization and thenpolymerizing the (alk)acrylamide monomer and carrying out the Mannichreaction simultaneously.

Formaldehydes suitable are typically selected from formaldehyde,paraformaldehyde, trioxane, aqueous formalin and mixtures thereof.Secondary amines suitable are selected from those containing from about2 to about 8 carbon atoms which are aliphatic, cyclic, straight chainedor branched.

The Mannich polymers produced by the above procedures are thenquaternized by reacting them with such quaternizing agents asmethylbromide, methyl iodide, ethyl chloride, methyl chloride, dimethylsulfate, benzyl chloride, benzyl bromide, alkyl chloride, and the likeunder known conditions.

The water soluble unstabilized QMM's treated in accordance with theprocess of the present invention are (alk)acrylamide-containingmicroparticles having an average particle size of from about 200 toabout 4000 Å, preferably about 300 to about 2000 Å, most preferablyabout 350 to about 1000 Å, which are substituted with at least 1 molepercent of quaternized tertiary aminomethyl groups and can berepresented by the following general formula: ##STR1## where x rangesfrom 0-50, y ranges from 0 to 99, z ranges from 1 to 100, x+y+z=100 andX represents an anion such as Cl⁻, Br⁻, I⁻, CH₃ SO₄ or SO₄ ⁻, Y is acopolymerizable monomer polymerization residue R and R¹ are residuesubstituents from a secondary amine and R² is alkyl C₁ -C₄), allyl oraralkyl (C₇ -C₁₁).

The QMM's are treated by (a) adding with mixing to the untreated QMM anacid such that the pH range of the resulting QMM microemulsion is fromabout 3.6 to about 4.8; preferably about 3.8 to about 4.6, and aformaldehyde scavenger, (b) adjusting the polymer content of the aqueousphase to about 10 to about 45 wt. percent, preferably about 20-40, wt.percent, and (c) heating the QMM microemulsion obtained in step (b) to atemperature of from about 40° to about 80° C. for from about 3 to about20 hours.

Any water-soluble acid may be used in the instant invention. The acid ispreferably employed as an aqueous solution and preferably comprises (i)an organic carboxylic acid, an inorganic acid or a combination thereofin an amount sufficient to provide a pH of from about 3.6 to about 4.8in the resulting emulsion; (ii) from about 0.01 to about 30 mole percentof a formaldehyde scavenger based on the total moles of quaternizedamino methylated acrylamide polymer microemulsion; and (iii) water in anamount such that when added to the microemulsion the resulting aqueousphase contains from about 10 to about 45 weight percent of quaternizedamino methylated acrylamide polymer microemulsion.

The acid, preferably an organic carboxylic acid, inorganic acid and/orcombination thereof, is used in sufficient quantity such that theresulting pH of the microemulsion is from 3.6 to 4.8, preferably3.8-4.6. The quantity of each individual acid or combination of acidsemployed in the stabilized solution is determined by the acidity (pka)or each individual acidic component. The total amount of acid used inthe practice of the present invention may vary from about 1 to about 40mole % based on the total number of moles of polymer present in themicroemulsion. The only limitation on the acid used is that it be inertwith respect to the ingredients which are present in the microemulsionsystem, i.e. emulsifier, polymer, oil and other generally addedingredients.

Acids which may be employed for use herein include, but are not limitedto, mono and multifunctional carboxylic acids such as acetic, maleic,fumaric, formic, acrylic, succinic, lactic, citric and the like;inorganic acids such as sulfurous, phosphoric, phosphorous and sulfuricacids as well as salts of these acids such as the alkali salts ofsulfurous acid, aluminum sulfate, aluminum chloride, sodium sulfate andthe like. Any combination of the above-mentioned acids may be employedas long as the QMM microemulsion after the addition of the stabilizersolution has a pH within the range set forth above.

The formaldehyde scavengers useful herein are those water-solublecompounds which have the capability to react with formaldehyde. Thesource of formaldehyde in the QMM's of the present invention resultsfrom unreacted formaldehyde or from labile formaldehyde components thatrelease formaldehyde. The quantity of formaldehyde scavenger used in thepresent invention ranges from about 0.01 to about 30 mole percent,preferably ranging from about 0.6 to about 15 mole percent, based on themoles of polymer in the microemulsion.

Formaldehyde scavengers include those known in the art, and include, butare not limited to, urea, substituted ureas such as ethylene urea,guanidine salts, dicyanidiamide, sulfurous acid and any of its alkalimetal salts such as sodium bisulfite, sodium metabisulfite and the like,as well as phosphorous acid and mixtures of any of the foregoing.

The quantity of water preferably used in the stabilizer solutions isselected such that the resulting aqueous phase of the microemulsioncontains from about 10 to about 43 weight percent polymer, based on theweight of the total aqueous phase, preferably from about 15-40 weightpercent, same basis.

The formaldehyde scavenger and the acid, preferably in the form of anaqueous solution, thereof, as described hereinabove, are then added tothe microemulsion with mixing. The resulting microemulsion is thenheated to a temperature ranging from about 40° to about 80° C. for atime of from about 3 to about 20 hours. The heating step can be carriedout immediately after addition of the acid, scavenger and/or water,however, it is also possible to delay the heating up to the desired timeof use of the microemulsion as a flocculant.

The stabilized QMM obtained after the heating step will successfullyinvert when added to water independent of the temperature or pH of thewater used. The QMM's produced by the process of the present inventionwill also have increased storage stability, and provide improveddewatering characteristics.

The polymers of the present invention can conveniently be employed asflocculants prepared in the form of dilute aqueous solutions. Thesesolutions can be prepared by inverting the treated microemulsion intowater, optionally but preferably, in the presence of a breakersurfactant, or by recovering the polymer from the microemulsion, such asby stripping or by adding the microemulsion to a solvent whichprecipitates the polymer, e.g., isopropanol or acetone, filtering offthe resultant solids, drying and redispersing in water. Themicroemulsion can also be stripped of water to increase the percentageof polymer solids thereof. When a breaker surfactant is used, it isadded to the microemulsion to help stabilize it during theacid/scavenger/water addition step and enable inversion of the emulsionthereafter. Sufficient breaker surfactant should be added so as toenable the inverted polymer in solution to reach its maximum solutionviscosity. Breaker surfactant may be added to the microemulsions beforequaterization of the Mannich polymer or immediately before addition ofthe acid.

Concentrating dispersions of suspended solids is carried out by addingan effective amount of the treated microemulsion after inversion to thesuspension to remove water and thereby produce an effluent of desiredcharacteristics.

The products produced by the process of this invention are useful infacilitating a wide range of solid-liquid separation operations. Thecationic polymers may be used in the dewatering of biologically treatedsuspensions, such as sewage and other municipal or industrial sludges,the drainage of cellulosic suspensions such as those found in paperproduction, e.g., paper waste, and settlement of various suspensions,i.e., refinery waste, food waste, etc.

BEST MODE OF COMMERCIAL PRODUCTION OF QUATERNIZED TERTIARY AMINOMETHYLACRYLAMIDE POLYMER MICROEMERSIONS

Subsequent to the filing of assignees prior applications for letterspatent for microemulsion polymers, significant work has been undertakenin perfecting the process and products disclosed therein. At the time ofthis subsequent filing, improvements representing the best modecontemplated for the manufacture of such products at the time of thisfiling and which are subject to the improvements set forth herein arepresented in the following eight (8) examples. These examples are in noway meant to limit the invention herein but are presented as examples ofthe best mode of making the subject polymer at the time of this filing.

PREPARATION OF POLYACRYLAMIDE (PAM) BACKBONE MICROEMULSION BackgroundExample 1

To 223 lbs of an organic solution containing 182 lbs of low odorparaffin oil, 29 lbs of Polyoxyethylene sorbitol fatty acid ester, 12.6lbs of Sorbitan sesquioleate is slowly added 219 lbs of a pH=3 aqueoussolution containing 100 lbs of acrylamide, 6 lbs of acetic acid, 0.2 lbsof isopropanol, 0.2 lbs ethylenediaminetetra-acetic acid tetra sodiumsalt, 0.15 lbs of a sodium bromate, 0.14 lbs of sulfuric acid and 112lbs of water. The resulting monomer emulsion is sparged for 60 minuteswith nitrogen. SO₂ gas is then bubbled in the emulsion at a ratemaintaining the rate of temperature increase around 2° C./min. allowinga maximum batch temperature of 65° C. Once the AMD conversion is greaterthan 99% the batch is cooled to 30° C. The result is 443 lbs of a clear,stable PAM microemulsion having an SV between 3.0 and 4.0 cps.

PREPARATION N,N-DIMETHYLAMINOMETHANOL (DMAM-S) Background Example 2

Paraformaldehyde 45 lbs (92%, 41 lbs real) is slowly added to an aqueousdimethylamine solution containing 64 lbs of real dimethylamine and 43lbs water while maintaining the temperature below 30° C. until thesolids dissolve. Dicyanamide 6 lbs and 7 lbs of sodium metabisulfite areadded maintaining the temperature below 35° C. affording 203 lbs ofDMAM-S.

PREPARATION OF PAM-MANNICH-75 Background Example 3

443 lbs of PAM microemulsion of Background Example 1 is placed in areaction vessel at ambient temperature. To this are slowly adding 89 lbsof low odor paraffin oil followed by 203 lbs of DMAM-S of BackgroundExample 2, the DMAM-S being added over a 1.5 hour period maintaining thetemperature between 30°-35° C. The resulting PAM-Mannich microemulsionis stirred at this temperature for an additional 16 hours. The resultingPAM-Mannich, 734 lbs is obtained as an opaque microemulsion.

QUATERNIZATION OF PAM-MANNICH OF BACKGROUND EXAMPLE 3 Background Example4

703 lbs of the PAM-Mannich of Background Example 3 is placed in astirred pressure reactor and the temperature adjusted to 25° C. To thisis added 84 lbs of methyl chloride at a rate maintaining the temperaturebelow 32° C. and the reactor pressure below 30 psi. The resultingmicroemulsion is stirred at this temperature for an additional 18 hours.After this time, the pH of the emulsion is between 5 and 6 and theexcess methyl chloride removed. To the resulting microemulsion is added14 lbs of a 23% sodium metabisulfate solution. If desirable a breakersurfactant (25 lbs of Surfonic N-95) may be added at this time.

The resulting product is a clear, stable quaternized Mannich PAMmicroemulsion having an average of 75±5% cationic charge as measured byinfrared analysis.

PREPARATION OF PAM-MANNICH-55 Background Example 5

443 lbs of PAM microemulsion of Background Example 1 is placed in areaction vessel at ambient temperature. To this are slowly adding 89 lbsof low odor paraffin oil and 144 lbs of DMAM-S of Background Example 2the DMAM-S being added over a 1.5 hour period maintaining thetemperature between 30°-35° C. The resulting PAM-Mannich microemulsionis stirred at this temperature for an additional 16 hours. 675 lbs ofPAM-Mannich microemulsion is obtained.

QUATERNIZATION OF PAM-MANNICH OF BACKGROUND EXAMPLE 5 Background Example6

675 lbs of the PAM-Mannich of Background Example 5 is placed in astirred pressure reactor and the temperature adjusted to 25° C. To thisis added 700 lbs of methyl chloride at a rate maintaining thetemperature below 32° C. and the reactor pressure below 30 psi. Theresulting microemulsion is stirred at this temperature for an additional18 hours. After this time the pH of the emulsion is between 5 and 6 andthe excess methyl chloride removed.

The resulting product is a quaternized Mannich PAM microemulsion havingan average of 55±3% cationic charge as measured by infrared analysis.

PREPARATION OF PAM-MANNICH-35 Background Example 7

443 lbs of PAM microemulsion of Background Example 1 is placed in areaction vessel at ambient temperature. To this are slowly adding 885lbs of low odor paraffin oil and 103 lbs of DMAM-S of Background Example2 over a 1.5 hour period maintaining the temperature between 30°-35° C.The resulting PAM-Mannich microemulsion is stirred at this temperaturefor an additional 16 hours. 633 lbs of PAM-Mannich is obtained.

QUATERNIZATION OF PAM-MANNICH OF BACKGROUND EXAMPLE 7 Background Example8

634 lbs of the PAM-Mannich of Background Example 7 is placed in astirred pressure reactor and the temperature adjusted to 25° C. To thisis added 81 lbs of methyl chloride at a rate maintaining the temperaturebelow 32° C. and the reactor pressure below 30 psi. The resultingmicroemulsion is stirred at this temperature for an additional 18 hours.After this time the pH of the emulsion is between 5 and 6 and the excessmethyl chloride removed.

The resulting product is a clear, stable quaternized Mannich PAMmicroemulsion having an average of 35±3% cationic charge as measured byinfrared analysis.

IONIC REGAIN ANALYSIS OF MICROEMULSION Background Example 9

An amount of a commercial production of American Cyanamid's Excel®flocculant comparable to the above referenced QMM-75 was added todeionized water and was gently stirred for two hours at ambienttemperature to form a 1% solution. The resulting solution had a pH of5.2. An aliquot of this solution was diluted to 0.1% with additionaldeionized water. The standard viscosity and cationic equivalent (CEQ) ofthe 0.1% solution were found to be 1.25 cps and 4.2 meq/g respectively.CEQ was measured by the technique described in J. Chem. Ed. 62(7),627(1985). A 100 g sample of the 0.1% solution was sheared for 10minutes at between 10,000-10,500 rpm in a Silverson homogenizer and theCEQ of the solution was measured to be 4.2 meq/g. The solution was thensheared for an additional 10 minutes in the same manner and the CEQ wasmeasured to be 4.1 meq/g. Accordingly the ionic regain (IR) of thesolution of polymer was found to be 0% wherein the ionic regain iscalculated by the formula:

    IR=(CEQ sheared--CEQ)×100/CEQ sheared

Subsequently, a second sample of the same product was made up to a 1%solution in deionized water whose pH had been adjusted to 7. Afterstirring for two hours, this sample had a measured standard viscosity of2.8 cps. This example demonstrates that the availability of cationiccharge on this polymer is independent of the attainment of maximumviscosity (13.8 percent thereof in this example) of the polymer insolution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples are set forth for purpose of illustration onlyand are not to be construed as limitations on the present inventionexcept as set forth in the appended claims. All parts and percentagesare by weight unless otherwise specified.

Standard Viscosity (SV) as used in the examples below is measured byadding 8 grams of a 0.2% aqueous polymer solution to 8.6 g of a 2Nsodium chloride solution, stirring the resulting mixture for 1 minuteand determining the viscosity at 25°±0.1° C. using a BrookfieldViscometer with a UL adapter at 60 rpm.

0.2% Aqueous polymer solutions expressed in the examples are prepared byadding with good agitation the appropriate quantity of the microemulsionto the appropriate amount of deionized water at 25°±2° C. The resultingsolution is then stirred for 2 hours before use. The pH of the resultingsolution, as referred to herein is defined as its natural pH. Whenreference is to SV at pH=7, this procedure for such a designationinvolves adjustment of the 0.2% polymer solution pH to 7 and maintaininga pH of 7 throughout the 2 hour stirring time.

The specified pH of the QMM microemulsions is obtained by stirring theemulsion at 25° C., immersion of a ROSS© combination electrode OrionModel #8102, and allowing the pH reading to attain equilibrium, normallyabout 10 minutes.

The following examples teach the preparation of the acid/scavengersolutions as well as the treated QMM's. In each example, C designates"comparative".

Part A. The treated QMM's used in Tables 3, 4, 5, 6, 8, 11, 12, 13, and15 are prepared as follows:

Acid/Scavenger Solutions

An appropriate quantity of deionized water is weighed into a suitablevessel containing a magnetic stir bar. The water containing vessel isplaced on a stir plate and at low speed an appropriate quantity ofscavenger is added. The solution is mixed until the scavenger is fullydissolved.

Then, an appropriate quantity of acid is added and stirred for a fewadditional minutes.

The compositions of the solutions are as follows:

    ______________________________________                                        1. Urea/Acetic Acid                                                           Urea                 2.6     parts                                            Glacial Acetic Acid  10.34   parts                                            Deionized Water      87.06   parts                                            Total                100.00  parts                                            2. Urea/Citric Acid                                                           Urea                 2.6     parts                                            Citric Acid          4.95    parts                                            Deionized Water      92.5    parts                                            Total                100.00  parts                                            3. Organic/Inorganic                                                          Sodium Metabisulfite 6.4     parts                                            Citric Acid          4.74    parts                                            Deionized Water      88.86   parts                                            Total                100.00  parts                                            ______________________________________                                    

Post Treatment

To a 50 parts of QMM-75 in a suitable vessel, are added 0.75 parts ofN-95 dropwise with good mixing. 10 Parts of the acid/scavenger solutionis fed into the vessel using a syringe pump over a 20 minute period andstirring is continued for an addition 10 minutes. Another 0.75 parts ofthe beaker emulsifiers is added to the batch.

Heat Treatment

The vessel, covered loosely, containing the resultant emulsion is placedin an oven at 65°-68° C. for 7-16 hours or 78° C. for 4 hours.

Part B. The treated QMM's used in Tables 1, 2, 7, 9, 10, 13, and 14 areprepared as follows:

Breaker emulsifier (3.76 parts) is added to QMM-55 or QMM-35 (301.33parts) with stirring. An appropriate quantity of acid/scavenger solution(see table below) is metered into the QMM. Breaker emulsifier (3.76parts) is added to the resultant QMM and this mixture is heated to 70°C. for 7 hours.

    ______________________________________                                        1. Urea/Acetic Acid                                                           Deionized water      77.7    parts                                            Glacial Acetic Acid  14.1    parts                                            Urea                 2.7     parts                                            Total                94.5    parts                                            2. Acetic Acid/Urea/Alum                                                      Deionized Water      65.9    parts                                            Glacial Acetic Acid  3.6     parts                                            Urea                 2.9     parts                                            Alum                 2.9     parts                                            Total                75.3    parts                                            3. Lactic Acid/Urea                                                           Deionized Water      69.1    parts                                            Lactic Acid          3.2     parts                                            Urea                 3.0     parts                                            Total                75.3    parts                                            ______________________________________                                    

                  TABLE 1                                                         ______________________________________                                        Effect of Varying Maleic Acid on the Treatment of 55% Cationicity             QMM at 22.2% Solids, 10 Mole % Urea and 70° C./7 Hours                        Mole % Acid                                                            Example                                                                              (on polymer)                                                                             SV (nat)   SV (pH 7)                                                                            Emulsion pH                               ______________________________________                                        1      2          1.70 (5.21)                                                                              2.1    4.7                                       2      5          2.57 (4.47)                                                                              3.11   4.3                                       3      10         1.27 (4.07)                                                                              1.52   3.73                                        4C   15         1.17 (3.83)                                                                              1.33   3.54                                        5C   20         1.13 (3.81)                                                                              1.3    3.24                                        6C   25         1.16 (3.58)                                                                              1.26   3.07                                      ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Effect of Varying Maleic Acid on the Treatment of 35% Cationicity             QMM at 19.5% solids, 15 Mole % Urea and 70° C./7 Hours                        Mole % Acid                                                            Example                                                                              (on polymer)                                                                             SV (nat)   SV (pH 7)                                                                            Emulsion pH                               ______________________________________                                        7      2.1        1.95 (4.63)                                                                              2.1    4.19                                      8      5.2        2.19 (4.23)                                                                              2.7    4.18                                      9      10.4       1.28 (4.00)                                                                              1.64   3.88                                      10C    15.6       1.16 (3.88)                                                                              1.72   3.49                                      11C    20.8       1.14 (3.75)                                                                              1.82   3.15                                      12C    26.0       1.14 (3.70)                                                                              1.36   2.99                                      ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Effect of Emulsion pH on Product as Measured by SV                            5 Mole % Urea, Various Acetic Acid Concentration,                             25% Polymer Solids at 75% QMM Cationicity                                     and 67° C./16 Hours Treatment                                          Exam- Mole % Acid                                                                              0.2% Solution                                                                            Emulsion                                                                             SV   SV                                    ple   on Polymer pH         pH     (nat)                                                                              (pH = 7.0)                            ______________________________________                                        13C.  1          4.9        5.2    1.8  2.0                                   14    10         4.28       4.56   2.6  2.62                                  15    20         4.25       4.38   2.77 2.70                                  16    30         4.25       4.28   2.80 2.84                                  17    40         4.20       4.17   2.74 2.74                                  18    50         4.08       4.15   2.79 2.74                                  19    70         3.80       3.90   2.0  2.40                                  ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Effect of Emulsion pH on Product as Measured by SV                            5 Mole % Urea, Various Citric Acid Concentrations at                          25% Polymer Solids at 75% QMM Cationicity and 67° C./16 Hours          Exam- Mole % Acid                                                                              0.2% Solution                                                                            Emulsion                                                                             SV   SV                                    ple   on Polymer pH         pH     (nat)                                                                              (pH = 7.0)                            ______________________________________                                        20C   1          4.69       5.0    1.6  1.7                                   21    3          4.00       4.4    2.6  2.8                                   22    5          3.7        4.1    2.6  2.9                                   23C   10         3.4        3.4    1.2  2.7                                   24C   15         3.2        3.1    1.2  2.6                                   25C   20         3.2        2.9    1.1  2.6                                   ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Effect of Emulsion pH on Product as Measured by SV                            5 Mole % Urea, Various Citric Acid Concentrations at                          25% Polymer Solids at 75% QMM Cationicity and 67° C./16 Hours          Exam- Mole % Acid                                                                              0.2% Solution                                                                            Emulsion                                                                             SV   SV                                    ple   on Polymer pH         pH     (nat)                                                                              (pH = 7.0)                            ______________________________________                                        26C   1          5.13       5.2    2.1  1.2                                   27    3          4.7        4.8    2.0  2.3                                   28    5          4.55       4.65   2.4  2.5                                   29    10         4.1        4.1    2.8  2.8                                   30    15         3.75       3.9    2.6  2.7                                   31    20         3.7        3.6    2.4  2.8                                   ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Effect of Acid/Scavenger and Temperature on                                   Emulsion QMM Breaking at 75% QMM Cationicity                                         %      Age      Time  pH    SV                                         Example                                                                              Solid  Temp (C.)                                                                              Hours (0.2%)                                                                              (cps)                                                                              Acid/Scavenger                        ______________________________________                                         .sup. 32C                                                                           30     --       --    5.5   1.40 --                                    33     24.4   60       16    4     2.30 25 mole % AA/                                                                 10 mole % urea                        34     24.4   60       16    4.26  2.44 25 mole % AA/                                                                 15 mole % urea                        35     24.4   65       16    3.98  2.91 25 mole % AA/                                                                 10 mole % urea                        36     24.4   65       16    4.27  2.94 25 mole % AA/                                                                 15 mole % urea                        37     24.4   70       16    3.98  2.94 25 mole % AA/                                                                 10 mole % urea                        38     24.4   70       16    4.32  2.99 25 mole % AA/                                                                 15 mole % urea                        39     24.4   80       3.67  3.98  2.70 25 mole % AA/                                                                 10 mole % urea                        40     24.4   80       3.67  4.04  2.62 5 mole % AA/                                                                  15 mole % urea                        41     24.4   65       16    4.26  2.59 12.5 mole %                                                                   Guanidine                                                                     Nitrate/12.5                                                                  mole % AA                             ______________________________________                                         AA = Acetic Acid                                                         

                  TABLE 7                                                         ______________________________________                                        Effect of Varying Urea on the Lactic Acid Treatment of 55%                    Cationicity QMM at 5 Mole % Acid, 22.2% Solids and 70°C./7 Hours              Mole % Urea                    Emulsion                                Example                                                                              (on polymer)                                                                             S.V. (pH Nat)                                                                             S.V. (pH 7)                                                                           pH                                      ______________________________________                                          42C  1          1.87 (4.61) 2.34    3.81                                    43     3          2.19 (4.52) 2.94    3.84                                    44     5          2.22 (4.51) 2.91    3.87                                    45     7          2.19 (4.62) 2.91    4.06                                    46     10         2.29 (4.68) 2.91    4.07                                    47     12.5       2.27 (4.74) 3.07    4.25                                    ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        Examples of Inorganic/Organic Mixed Acids                                     On QMM's At 75% Cationicity                                                          Solids                  pH    S.V.                                     Example                                                                              %         Stabilizer System                                                                           (0.2%)                                                                              (cps)                                    ______________________________________                                         .sup. 48C                                                                            30.37    --            7.0   1.80                                     49     25.0      NaHSO.sub.3 25.0 m %                                                                        4.36  2.25                                     50     25.0      NaHSO.sub.3 18.5 m %                                                                        4.6   2.37                                     51     25.0      NaHSO.sub.3 15.0 m %                                                                        4.6   2.17                                      .sup. 52C                                                                           25.0      NaHSO.sub.3 10.0 m %                                                                        4.99  1.74                                      .sup. 53C                                                                           25.0      NaHSO.sub.3 18.5 m %                                                          Citric 5.0 m %                                                                              3.67  1.36                                     54     25.0      NaHSO.sub.3 18.5 m %                                                          Citric 2.4 m %                                                                              3.95  2.10                                     55     25.0      NaHSO.sub.3 18.5 m %                                                          Citric 1.8 m %                                                                              4.17  2.30                                     56     25.0      NaHSO.sub.3 18.5 m %                                                          Citric 1.2 m %                                                                              4.15  2.30                                     57     25.0      NaHSO.sub.3 18.5 m %                                                          Citric 1.2 m %                                                                              4.08  2.32                                     58     25.0      NaHSO.sub.3 18.5 m %                                                          Citric 0.8 m %                                                                              4.25  2.20                                     59     25.0      NaHSO.sub.3 18.5 m %                                                          Alum 0.85 m % 4.01  2.24                                     60     25.0      NaHSO.sub.3 18.5 m %                                                          Alum 0.073 m %                                                                              4.09  2.15                                      .sup. 61C                                                                           25.0      MBS 0.5 m %                                                                   Citric 2.0 m %                                                                              4.56  1.87                                     62     25.0      MBS 1.0 m %                                                                   Citric 2.0 m %                                                                              4.36  2.15                                     63     25.0      MBS 2.0 m %                                                                   Citric 2.0 m %                                                                              4.38  2.64                                     64     25.0      MBS 3.0 m %                                                                   Citric 2.0 m %                                                                              4.35  2.70                                     65     25.0      MBS 4.0 m %                                                                   Citric 2.0 m %                                                                              4.33  2.56                                     66     25.0      MBS 3.0 m %                                                                   Citric 2.0 m %                                                                GHCl 1.0 m %  4.30  3.09                                     67     25.0      MBS 3.0 m %                                                                   Citric 2.0 m %                                                                GHCl 3.0 m %  4.26  2.94                                     68     25.0      MBS 4.0 m %                                                                   Citric 2.0 m %                                                                GHCl 5.0 m %  4.27  2.84                                     ______________________________________                                         MBS = Sodium Metabisulfate                                                    GHCl = Guanidine Hydrochloride                                           

                  TABLE 9                                                         ______________________________________                                        Examples of Use of Organic/Inorganic Acids on                                 QMM at 35 Percent Cationicity Using 10 Mole % Urea                                   Acid     Alum                    Emulsion                              Example                                                                              Mole %   Mole %  S.V. (Nat)                                                                            S.V. (pH 7)                                                                           pH                                    ______________________________________                                          69C  2.4      0.0     1.79    2.02    4.44                                  70     2.4      0.16    2.10    2.44    4.11                                  71     2.4      0.32    2.27    2.67    4.11                                    72C  2.4      0.64    1.24    1.38    4.04                                    73C  2.4      0.96    1.16    1.18    3.92                                  ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                        Effect of Temperature on Treatments on QMM of 55% Cationicity                 at 21.7% Solids at 10 Mole % Urea and Various Lactic Acid Levels                     Acid   Alum                                                                   Mole   Mole     Temp. °C./                                                                     SV   SV    Emulsion                            Example                                                                              %      %        Time hrs                                                                              (Nat)                                                                              (pH 7)                                                                              pH                                  ______________________________________                                        74     5      0        80/4    2.62 2.87  4.2                                 75     5      0        70/7    2.49 3.09  4.29                                76     5      0.08     80/4    2.74 2.87  4.18                                77     5      0.08     70/7    2.89 3.02  4.3                                 78     5      0.2      80/4    2.86 3.11  4.01                                79     5      0.2      70/7    2.82 3.02  4.34                                80     5      0.4      80/4    2.84 3.19  3.67                                81     5      0.4      70/7    2.65 3.06  4.25                                 .sup. 82C                                                                           5      1.6      80/4    1.32 1.77  3.18                                83     5      1.6      70/7    1.20 1.44  3.69                                 .sup. 84C                                                                           5      1.6       60/16  1.16 1.57  2.93                                ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        Thermal Stability of Treated QMM Microemulsion                                at 25%, 26% and 27% Solids                                                    Using 5 Mole % Urea and 3 Mole % Citric Acid                                          25% Solids    26% Solids    27% Solids                                              SV     SV     SV   SV     SV   SV                               Example                                                                              Day    (Nat)  (pH 7) (Nat)                                                                              (pH 7) (Nat)                                                                              (pH 7)                           ______________________________________                                        85     0      2.89   2.96   2.62 2.91   2.20 2.80                             86     1      3.02   3.57   3.09 3.66   2.22 3.09                             87     4      3.24   2.87   2.97 2.99   2.44 2.65                             88     5      3.36   3.26   2.86 3.11   2.37 2.67                             89     8      3.21   3.52   2.94 3.02   2.27 2.34                             90     10     3.21   3.37   2.76 3.09   2.20 2.45                             ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        Thermal Stability of Treated QMM Microemulsion at 50° C.               Using 20 Mole % Acetic Acid and 8 Mole % Ethylene Urea                        Example % Solids  pH (0.2%)  SV (Nat)                                                                              SV (pH 7)                                ______________________________________                                         91*    27.0      4.22       2.56    2.84                                     91      27.0      4.47       2.47    2.72                                     93      27.0      4.52       2.56    2.69                                     94      27.0      4.66       2.57    2.70                                     95      27.0      4.60       2.52    2.65                                     96      27.0      4.62       2.50    2.65                                     97      27.0      4.61       2.54    2.64                                     98      27.0      4.53       2.56    2.65                                     99      27.0      4.50       2.54    2.61                                     100     27.0      4.55       2.49    2.62                                     101     27.0      4.65       2.40    2.49                                     ______________________________________                                         *treatment was 80° C. for 4 hours.                                

                  TABLE 13                                                        ______________________________________                                        Stability of Various QMM At Ambient Temperature                               Exam- QMM-Cat.  Age     SV   SV    Post                                       ple   %         (mos.)  (Nat)                                                                              (pH 7)                                                                              Treatment Conditions                       ______________________________________                                        102   75        fresh   2.47 2.65  20 mole % acetic acid                      103             1       2.56 2.60  8 mole % ethylene                                                             urea                                       104             4       2.50 2.62  80° C./4 hours                      105             5       2.40 2.68                                             106             6       2.40 2.60                                             107             7.5     2.45 --                                               108             9       2.34 --                                               109   55        fresh   1.85 2.5   36 mole % acetic acid                      110             2.25    2.2  2.61  10 mole % urea                             111             4.5     2.37 2.56  70° C./5 hours                      112             5.25    2.39 2.47                                             113             6.25    2.44 2.54                                             114             7.25    2.64 2.62                                             115             10.75   2.44 2.35                                             116             11.75   2.54 2.37                                             117   55        fresh   2.37 2.79  36 mole % acetic acid                      118             3.75    2.52 2.79  10 mole % urea                             119             5.25    2.45 2.65  0.1 mole % alum                            120             6.25    2.74 2.84  70° C./5 hours                      121             9.75    2.49 2.64                                             122             10.75   2.49 2.54                                             123   35        fresh   2.81 3.04  36 mole % acetic acid                      124             1       2.82 2.97  10 mole % urea                             125             2       2.74 2.91  0.1 mole % alum                            126             5.5     2.57 2.72  70° C./5 hours                      127             6.5     2.56 2.62                                             128   17        fresh   2.70 2.92  36 mole % acetic acid                      129             1       2.84 2.97  10 mole % urea                             130             2       2.94 2.77  0.1 mole % alum                            131             5.5     2.65 2.72  70° C./5 hours                      132             6.5     2.61 2.65                                             ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                        Effect of Varying Post-Addition of Water to 55% QMM                           29.9 Mole % Acetic Acid on Polymer                                                   Wt. % added                                                                              %             SV     % Polymer                              Example                                                                              H.sub.2 O (on emul.)                                                                     Solids  SV (Nat)                                                                            (pH 7) Ag. Phase                              ______________________________________                                        133    19.3       20.15   2.84  3.02   33.3                                   134    15.0       21.05   2.37  2.70   34.8                                   135    12.0       21.73   2.35  2.50   35.9                                   136    10.0       22.20   1.95  2.17   36.7                                   137    5.0        23.49   1.42  1.48   38.8                                   ______________________________________                                    

                                      TABLE 15                                    __________________________________________________________________________    Effect of Polymer and Water Ratio of Stabilized QMM                                    Example No.                                                                   138 139 140 141 142  143 144                                         __________________________________________________________________________    E (wt.)  50  55  56  58  60   62  64                                          B (wt.)  --  5   6   8   10   12  14                                          A (wt.)  30.46                                                                             35.46                                                                             36.46                                                                             38.46                                                                             40.46                                                                              42.46                                                                             44.46                                       O (wt.)  19.54                                                                             19.54                                                                             19.54                                                                             19.54                                                                             19.54                                                                              19.54                                                                             19.54                                       A (%)    61  64.5                                                                              65.1                                                                              66.3                                                                              67.4 68.5                                                                              69.5                                        O (%)    39  35.5                                                                              34.9                                                                              33.7                                                                              32.6 31.5                                                                              30.5                                        A/O      1.558                                                                             1.815                                                                             1.866                                                                             1.968                                                                             2.07 2.173                                                                             2.27                                        Polymer Solids (%)                                                                     50.54                                                                             43.42                                                                             42.22                                                                             40.0                                                                              38.05                                                                              36.26                                                                             34.63                                       in Aqueous Phase                                                               Polymer (wt. %)                                                                        49.42                                                                             45.53                                                                             44.71                                                                             43.15                                                                             41.69                                                                              40.33                                                                             39.05                                      H.sub.2 O (wt. %)                                                                      50.58                                                                             54.47                                                                             55.29                                                                             56.85                                                                             58.67                                                                              59.67                                                                             60.95                                       N-95     1.5 1.5 1.5 1.5 1.5  1.5 1.5                                         Solids (%)                                                                             29.9                                                                              27.25                                                                             26.78                                                                             25.88                                                                             25.04                                                                              24.25                                                                             23.51                                       Emulsion pH                                                                            5.5 4.38                                                                              4.45                                                                              4.45                                                                              4.45 4.45                                                                              4.45                                        pH (0.2%)                                                                              5.4 4.38                                                                              4.31                                                                              4.16                                                                              4.17 4.11                                                                              4.11                                        SV (cps) 1.19                                                                              2.44                                                                              2.64                                                                              2.84                                                                              2.84 2.84                                                                              2.84                                        pH (0.2%)                                                                              7.0 7.0 7.0 7.0 7.0  7.0 7.0                                         SV (cps) 2.59                                                                              2.84                                                                              2.87                                                                              2.87                                                                              2.87 2.87                                                                              2.87                                        __________________________________________________________________________     a. E (wt.): wt. of QMM emulsion.                                              b. B (wt.): wt. of stabilizer added.                                          c. A (wt.): wt. of aqueous phase.                                             d. O (wt.): wt. of oil phase.                                                 e. A (%): wt (%) of Aqueous.                                                  f. O%: wt (%) of oil phase                                                    g. A: wt. ration of aqueous phase and oil phase.                              h. Postadded N95 and LOPS are not included.                                   i. Polymer solids (%) in aqueous phase and polymer/H.sub.2 O ratio in         stabilized QMM are calculated using 5 mole % urea and 3 mole % citric         stabilizer system.                                                       

                                      TABLE 16                                    __________________________________________________________________________    Typical Municipal Waste Treatment Facility*                                                 Average                                                                            Lbs./Ton                                                                           Floc.                                                                            10 Sec.   Cake                                     Example                                                                            Polymer  Time/Min.                                                                          Real Size                                                                             Drainage                                                                           Filtrate                                                                           Solids                                   __________________________________________________________________________    145C Untreated Polymer                                                                      30   18   <1 94   Black                                                                              --                                                                       Particles                                     146C          60   18   <1 94   Black                                                                              --                                                                       Particles                                     147C          120  18   <1 94   Black                                                                              --                                                                       Particles                                     148C          30   80   1  156  Slt. 27.6                                                                     Fines                                         150  Treated Polymer                                                                        30   18   4  182  Slt. 26.0                                                                     Fines                                         143           120  18   5  166  Slt. 26.1                                                                     Fines                                         __________________________________________________________________________     *Sludge Solids = 1.55%; pH = 7.2                                         

EXAMPLES 151-154

The procedure of Example 2 is again followed except that the acid isreplaced by sufficient amounts of 151) an amino acid, 152) B-rescorcilicacid, 153) phosphoric acid and 154) acrylic acid. In each instance,similar results are achieved.

EXAMPLE 155

The procedure of Example 36 is again followed except that the scavengeris replaced by a sufficient amount of melamine. Similar results areachieved.

EXAMPLES 156-163

The procedure of Example 16 is again followed except that an equivalentpercentage of acrylamide is replaced by 156) diallyldimethyl ammoniumchloride (30%), 157) N,N-dimethyl-acrylamide (8%), 158)N-vinylpyrrolidone (2%), 159) acrylic acid (10%), 160)2-acrylamido-2-methylpropane sulfonic acid (20%), 161)N,N-dimethylaminopropyl acrylamide (20%), 162) methylenebisacrylamide(0.001%), and 163) acrylonitrile (27%). In each instance, substantiallyequivalent results are achieved.

We claim:
 1. A method for treating a quaternized amino methylatedacrylamide polymer microemulsion which comprises:(a) adding to saidquaternized amino methylated acrylamide polymer microemulsion:(i)organic carboxylic acid in an amount sufficient to provide a pH of fromabout 3.6 to about 4.8 in the microemulsion; (ii) from about 0.01 toabout 30 mole percent of a formaldehyde scavenger compound, based on thetotal moles of quaternized amino methylated acrylamide polymermicroemulsion; and (iii) water in an amount such that the aqueous phaseof the resulting microemulsion comprises from about 10 to about 45weight percent of quaternized amino methylated acrylamide polymer; and(b) heating the microemulsion obtained in step (a) to a temperature offrom about 40° to about 80° C. for from about 3 to about 20 hours.
 2. Amethod as defined in claim 1 wherein the polymer amino methylatedpolymer microemulsion acrylamide comprises (alk)acrylamide polymericmicroparticles, said (alk)acrylamide polymer being substituted with atleast about 1 mole percent of tertiary aminomethyl groups and having anaverage particle size of from about 200 to about 4000 Å in diameter. 3.A method as defined in claim 1 wherein said amino methylated acrylamidepolymer is a copolymer of an acrylamide and an ethylenically unsaturatedcomonomer.
 4. A method as defined in claim 1 wherein said alkacrylamidepolymer comprises polyacrylamide.
 5. A method as defined in claim 2wherein said tertiary amino methyl groups are a reaction product of anamide group with a formaldehyde and a secondary amine.
 6. A method asdefined in claim 5 wherein the secondary amine is selected fromdimethylamine, methylethylamine, diethylamine, amylmethylamine,dibutylamine, dibenzylamine, piperidine, morpholine, ethanolmethylamine,diethanolamine or mixtures thereof.
 7. A method as defined in claim 6wherein said secondary amine comprises dimethylamine.
 8. A method asdefined in claim 5 wherein said formaldehyde is selected from aqueousformaldehyde, formalin, paraformaldehyde, trioxane or mixtures thereof.9. A method as defined in claim 1 wherein said (alk)acrylamide polymeris quaternized with dimethyl sulfate, methyl bromide, methyl chloride,ethyl chloride, methyl iodide, benzyl chloride, benzyl bromide, allylchloride or mixtures thereof.
 10. A method as defined in claim 1 whereinsaid organic carboxylic acid is selected from acetic acid, succinicacid, lactic acid, maleic acid, fumaricacid, formic acid, acrylic acid,citric acid and mixtures thereof.
 11. A method as defined in claim 1wherein said formaldehyde scavenger is selected from urea, ethyleneurea, guanidine salts, sulfurous acid, sodium bisulfite, sodiummetabisulfite, phosphorous acid and mixtures thereof.
 12. A method asdefined in claim 1 wherein said formaldehyde scavenger is employed in anamount ranging from about 0.6 to about 15 mole % based on the totalmoles of quaternized amino methylated acrylamide polymer microemulsion.13. A method as defined in claim 1 wherein said pH ranges from about 3.8to about 4.6.
 14. A process for flocculating suspended solids comprisingadding to said suspended solids a synthetic polymer flocculant materialcomprising a solution of a polymer produced by a method for treating aquaternized amino methylated acrylamide polymer microemulsion whichcomprises:(a) adding to said quaternized amino methylated acrylamidepolymer microemulsion:(i) organic carboxylic acid in an amountsufficient to provide a pH of from about 3.6 to about 4.8 in themicroemulsion; (ii) from about 0.01 to about 30 mole percent of aformaldehyde scavenger compound, based on the total moles of quaternizedamino methylated acrylamide polymer microemulsion; and (iii) water in anamount such that the aqueous phase of the resulting microemulsioncomprises from about 10 to about 45 weight percent of quaternized aminomethylated acrylamide polymer; and (b) heating the microemulsionobtained in step (a) to a temperature of from about 40° to about 80° C.for from about 3 to about 20 hours.
 15. A process as defined in claim 14wherein the polymer amino methylated polymer microemulsion acrylamidecomprises (alk)acrylamide polymeric microparticles, said (alk)acrylamidepolymer being substituted with at least about 1 mole percent of tertiaryaminomethyl groups and having an average particle size of from about 200to about 4000 Å in diameter.
 16. A process as defined in claim 14wherein said amino methylated acrylamide polymer is a copolymer of anacrylamide and as ethylenically unsaturated comonomer.
 17. A process asdefined in claim 14 wherein said alkacrylamide polymer comprisespolyacrylamide.
 18. A process as defined in claim 15 wherein saidtertiary amino methyl groups are a reaction product of an amide groupwith a formaldehyde and a secondary amine.
 19. A process as defined inclaim 18 wherein secondary amine is selected from dimethylamine,methylethylamine, diethylamine, amylmethylamine, dibutylamine,dibenzylamine, piperidine, morpholine, ethanolmethylamine,diethanolamine or mixtures thereof.
 20. A process as defined in claim 19wherein said secondary amine comprises dimethylamine.
 21. A process asdefined in claim 18 wherein said formaldehyde is selected from aqueousformaldehyde, formalin, paraformaldehyde, trioxane or mixtures thereof.22. A process as defined in claim 14 wherein said (alk)acrylamidepolymer is guaternized with dimethyl sulfate, methyl bromide, methylchloride, ethyl chloride, methyl iodide, benzyl chloride, benzylbromide, allyl chloride or mixtures thereof.
 23. A process as defined inclaim 14 wherein said organic carboxylic acid is selected from aceticacid, succinic acid, lactic acid, maleic acid, fumaric acid, formicacid, acrylic acid, citric acid and mixtures thereof.
 24. A process asdefined in claim 23 wherein said formaldehyde scavenger is selected fromurea, ethylene urea, guanidine salts, sulfurous acid, sodium bisulfite,sodium metabisulfite, phosphorous acid and mixtures thereof.
 25. Aprocess as defined in claim 23 wherein said formaldehyde scavenger isemployed in an amount ranging from about 0.6 to about 15 mole % based onthe total moles of guaternized amino methylated acrylamide polymermicroemulsion.
 26. A process as defined in claim 14 wherein said pHranges from about 3.8 to about 4.6.
 27. A method as claimed in claim 1,wherein said organic carboxylic acid is comprised of a mixture oforganic carboxylic acid and inorganic acid having a molar excess oforganic carboxylic acid.
 28. A method as claimed in claim 27, whereinsaid inorganic acid is aluminum sulfate or aluminum chloride.
 29. Aprocess as claimed in claim 14, wherein said organic carboxylic acid iscomprised of a mixture of organic carboxylic acid and inorganic acidhaving a molar excess of organic carboxylic acid.
 30. A process asclaimed in claim 29, wherein said inorganic acid is aluminum sulfate oraluminum chloride.